Ion implantation is a standard technique for introducing conductivity-altering impurities into a workpiece. A desired impurity material is ionized in an ion source, the ions are accelerated to form an ion beam of prescribed energy, and the ion beam is directed at the surface of the workpiece. The energetic ions in the beam penetrate into the bulk of the workpiece material and are embedded into the crystalline lattice of the workpiece material to form a region of desired conductivity.
Recently, higher temperature implants, such as above 100° C., have shown promise. For example, FinFET amorphization implants have shown the potential for single crystal regrowth when performed at temperatures exceeding 100° C. These recited temperatures are those of the workpiece itself. Techniques for workpiece temperature measurement are limited by the requirements of the processing environment. For example, thermocouples attached to the workpiece are impractical. Alternatively, thermocouples mounted to the platen are of limited use, as the temperature of the platen may differ from that of the workpiece due to problems associated with establishing good thermal contact between the platen and the workpiece. Additionally, the optical properties of silicon make the application of common infrared techniques difficult or impossible.
Thus, any method that allows for calibration and measurement of the temperature of a workpiece in a processing chamber would be beneficial.